Historic and Spatial Variation of Lake Whitefish Maturation Schedules
Grant: # 0662
Grant Amount: $107,290.13
Board Decision Year: 2005
University of Michigan - Cooperative Institute for Limnology and Ecosystem Research (Ann Arbor)
Cooperative Institute for Limnology and Ecosystem Research
Hook, Tomas ([email protected]) (734) 741-2388
GLFT - Ecosystem Health and Sustainable Fish Populations-D - Ecological and biological fisheries research to inform management
Project Details
This project involved exploration of spatial and temporal variation in maturation
schedules of Great Lakes lake whitefish (Coregonus clupeaformis). The purpose of the
project was essentially two-fold. First, to analyze extant data on lake whitefish
maturations schedules in lakes Michigan, Huron and Superior. Second, to use ecogenetic individual based models to explore how ecological processes and anthropogenic
activities (e.g., size-selective fisheries harvest) may shape genetically determined
maturation schedules and growth rates.
We analyzed maturation data collected by the Chippewa-Ottawa Resource Authority
(Michigan, Huron and Superior), Ontario Ministry of Natural Resources (Huron) and
Michigan Department of Natural Resources (Michigan and Superior). We estimated ages
and lengths at 50% maturity, age-specific maturation ogives (age-specific probability of
being mature), and midpoints of probabilistic maturation reaction norms (PMRN; a
metric that accounts for plastic effects of growth and mortality). These different
maturation indices varied significantly among sexes and systems. Notably, midpoints of
lake-sex-age-specific estimates of PMRN were smallest for Lake Michigan fish,
intermediate for fish in the main basin of Lake Huron, and largest for fish in Lake
Huron’s Georgian Bay and Lake Superior. These spatial patterns in PMRN suggest that
there is intrinsic variation in maturation schedules of lake whitefish from different
regions of the Great Lakes. Recently, with the invasion of dreissend mussels and the
collapse of Diporeia (an historically important prey for lake whitefish) the age at 50%
maturity in lakes Huron and Michigan has increased. However, age-specific PMRNs
have not expressed similar temporal trends, suggesting that shifts in age at 50% maturity
are primarily plastic responses to limited food resources.
We developed and applied multi-generational eco-genetic models to consider how
ecological processes and anthropogenic-induced selection pressures (e.g., size-selective
fishing) may influence phenotypically plastic life history traits; growth and maturation
schedules (i.e., traits whose expression are determined by both genetic factors and
ecological interactions). We initially focused on a complex, detailed model of lake
whitefish. However, the application and interpretation of such a complex model was not
straightforward. Thus, we also developed a less complex, generalized model. Our
models are demonstrative of the potential influence of both anthropogenic and ecological
factors (mortality rate, density-dependent growth) and the interactive effects of growth
and maturation on the inheritance of these two life-history traits.
Documents
Final Report
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